Chemical catalytic vapor deposition (CCVD) synthesis of carbon nanotubes by decomposition of ethylene on metal (Ni, Co, Fe) nanoparticles

A simple method for producing unsupported nickel catalyst that can be used to synthesize multi-wall carbon nanotubes (MWNT) has been developed. The yield of purified MWNTs is about 1.8 g_mwnt/(g_cat×h).     

Galilei’s relativity principle for a system of reaction-convection-diffusion equations

The representations of the Galilean algebra and its extensions relative to which the system of nonlinear reaction-convection-diffusion equations can be invariant are investigated. The kinds of nonlinearities at which this system is invariant relative to those algebras are determined to within continuous equivalence transformations.     

A micromechanically motivated diffusion-based transient network model and its incorporation into finite rubber viscoelasticity

This paper presents the development of a physical-based constitutive model for the representation of viscous effects in rubber-like materials. The proposed model originates from micromechanically motivated diffusion processes of the highly mobile polymer chains described within the formalism of Brownian motion. Following the basic assumption of accounting for the elastic and the viscous effects in rubber viscoelasticity by their representation through a separate elastic ground network and several viscous subnetworks, respectively, the kinetic theory of rubber elasticity is followed and extended to represent also the viscous contribution in this work. It is assumed that the stretch probability of certain chain segments within an individual viscous subnetwork evolves based on the movement of the chain endpoints described by the Smoluchowski equation extended in this work from non-interacting point particles in a viscous surrounding to flexible polymer chains. An equivalent tensorial representation for this evolution is chosen which allows for the closed form solution of the macroscopic free energy and the macroscopic viscous overstress based on a homogenization over the probability space of the introduced micro-objects. The resulting model of the viscous subnetwork is subsequently combined with the non-affine micro-sphere model and applied in homogeneous and non-homogeneous tests. Finally, the model capacity is outlined based on a comparison with in the literature available experimental data sets.     

Triangulenes: From Precursor Design to On-Surface Synthesis and Characterization

Triangulene and its higher homologues are a class of zigzag-edged triangular graphene molecules (ZTGMs) with high-spin ground states. These open-shell molecules are predicted to host ferromagnetically coupled edge states with net spin values scaling with molecular size and are therefore considered promising candidates for future molecular spintronics applications. Unfortunately, the synthesis of unsubstituted [n]triangulenes and the direct observation of their edge states have been a long-standing challenge due to a high reactivity towards oxygen. However, recent advances in precursor design enabled the on-surface synthesis and characterization of unsubstituted [3]-, [4]-, and [5]triangulene. In this Minireview, we will highlight key aspects of this rapidly developing field, ranging from the principles of precursor design to synthetic strategies and characterization of a homologous series of triangulene molecules synthesized on-surface. We will also discuss challenges and future directions.     

The algebraic classification of nilpotent Tortkara algebras

Abstract

We classify all complex 6-dimensional nilpotent Tortkara algebras.

Communicated by Alberto Facchini     

The first studies of a tetrathiafulvalene-sigma-acceptor molecular rectifier

Langmuir-Blodgett monolayers of a donor-acceptor diad TTF-sigma-(trinitrofluorene) (8) with an extremely low HOMO-LUMO gap (0.3 eV) have been used to create molecular junction devices that show rectification behavior. By virtue of structural similarities and position of molecular orbitals, 8 is the closest well-studied analogue of the model Aviram-Ratner unimolecular rectifier (TTF-sigma-TCNQ). Compressing the monolayer results in aligning the molecules, and is followed by a drastic increase in the rectification ratio. The direction of rectification depends on the electrodes used and is different in n-Si/8/Ti and Au/8/C16H33S-Hg junctions. The molecular nature of such behavior was corroborated by control experiments with fatty acids and by reversing the rectification direction with changing the molecular orientation (Au/D-sigma-A versus Au/A-sigma-D).     

Synthesis of oligosiloxane methacrylates and their application to anaerobic sealants

The synthesis of oligosiloxane methacrylates via the transesterification of oligomethoxyphenylmethylsiloxanes by 1,2-hydroxyethyl methacrylate is described. The dependences of the properties of synthesized oligomers on the content of methacrylate fragments are studied. The possibility of creating thermally stable anaerobic sealants with the required properties is shown on their basis.     

S掺杂纳米多孔碳的光催化活性:表面化学和孔隙率的重要性(英文)

This minireview summarizes our recent findings on the photoactivity of S-doped nanoporous carbons. The materials were either synthesized from the sulfur-containing polymers or obtained by heat treatment of commercial carbon with hydrogen sulfide. Their surface was extensively charac terized from the points of view of its surface chemistry, porosity, morphology, and electronic properties. The carbons showed enhanced activity towards oxidation of arsine and removal of diben-zothiophenes from model diesel fuel. The latter were oxidized to various oxygen containing intermediates and the cleavage of C–C bonds in aromatic ring was detected when carbon with adsorbed species was exposed to UV or visible light. Irradiation resulted in generation of photocurrent in a broad range of wavelength. The presence of sulfur led to the reduction of oxygen and contributed to an increased capacitive performance. We link these effects to the presence of reduced sulfur in the small pores which enhances the dispersive interactions via inducing a positive charge to carbon atoms, to sulfur in oxygenated forms which contribute to Faradaic reactions and increase the polar interactions, and to the hydrophobicity of a surface in small pores where oxygen can be reduced by excited electrons from chromophoric-like sulfur containing groups.